The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
VAP-1 is a human endothelial cell adhesion molecule that has several unique properties that distinguish it from the other inflammation-related adhesion molecules. One of the most interesting features of VAP-1 is a catalytic extracellular domain which contains a monoamine oxidase activity (Smith, D. J., et al., J. Exp. Med. 188:17-27 (1998)).
The cloning and sequencing of the human VAP-1 cDNA revealed that it encodes a transmembrane protein with homology to a class of enzymes called the copper-containing amine oxidases (E.C. 1.4.3.6). Enzyme assays have shown that VAP-1 possesses a monoamine oxidase (MAO) activity which is present in the extracellular domain of the protein (Smith, D. J., et al., J. Exp. Med. 188:17-27 (1998)). Thus, VAP-1 is an ecto-enzyme. Analysis of the VAP-1 MAO activity showed that VAP-1 belongs to the class of membrane-bound MAO's termed semicarbazide-sensitive amine oxidases (SSAO). These are distinguished from the widely distributed mitochondrial MAO-A and B flavoproteins by amino acid sequence, cofactor, substrate specificity and sensitivity to certain inhibitors. However, certain substrates and inhibitors are common to both SSAO and MAO activities. The mammalian SSAO's can metabolize various monoamines produced endogenously or absorbed as dietary or xenobiotic substances. They act principally on primary aliphatic or aromatic monoamines such as methylamine or benzylamine (Lyles G. A., Int. J. Biochem. Cell Biol, 28:259-274 (1996)). Thus, VAP-1 located on the vascular endothelial cell surface can act on circulating primary monoamines with the following reaction pathway.RNH2+O2+H2O—>RCHO+H2O2+NH3 
The physiological substrates of VAP-1 SSAO in man have not been clearly identified. However, methylamine is a good substrate for VAP-1 SSAO. Methylamine is a product of various human biochemical pathways for the degradation of creatinine, sarcosine and adrenaline, and is found in various mammalian tissues and in blood. It can also be derived from the diet by gut bacterial degradation of dietary precursors. The concentration of methylamine in the blood can be increased in certain physiological and pathological situations such as diabetes. Another potential physiological substrate is aminoacetone.
VAP-1 SSAO activity has been proposed to be directly involved in the pathway of leukocyte adhesion to endothelial cells by a novel mechanism involving direct interaction with an amine substrate presented on a VAP-1 ligand expressed on the surface of a leukocyte (Salmi et al. Immunity, vol. 14, pp. 265-276 (2001)). This publication describes the direct involvement of VAP-1 SSAO activity in the process of adhesion of leukocytes to endothelium. Thus inhibitors of VAP-1 SSAO activity could be expected to reduce leukocyte adhesion in areas of inflammation and thereby reduce leukocyte trafficking into the inflamed region and therefore the inflammatory process itself.
In human clinical tissue samples expression of VAP-1 is induced at sites of inflammation. This increased level of VAP-1 can lead to increased production of H2O2 generated from the action of the VAP-1 SSAO extracellular domain on monoamines present in the blood. This generation of H2O2 in the localized environment of the endothelial cell could initiate other cellular events. H2O2 is a known signaling molecule that can upregulate other adhesion molecules and this increased adhesion molecule expression may lead to enhanced leukocyte trafficking into areas in which VAP-1 is expressed. It also may be that other products of the VAP-1 SSAO reaction could have biological effects also contributing to the inflammatory process. Thus the products of the VAP-1 SSAO activity may be involved in an escalation of the inflammatory process which could be blocked by specific SSAO inhibitors.
VAP-1 SSAO may be involved in a number of other pathological conditions associated with an increased level of circulating amine substrates of VAP-1 SSAO. The oxidative deamination of these substrates would lead to an increase in the level of toxic aldehydes and oxygen radicals in the local environment of the endothelial cell which could damage the cells leading to vascular damage. It has been proposed that the vasculopathies such as retinopathy, neuropathy and nephropathy could be treated with specific inhibitors of SSAO activity.
Takahashi, H, et al., Yakugaku Zasshi 101(12):1154-1156 (1981) report the synthesis of a number of N-alkylaminoephedrines, including N-(isopropylideneamino)-ephedrine or R,S-(+)-(2-hydroxy-1-methyl-2-phenylethyl)methylhydrazone-2-propanone. These hydrazone compounds were synthesized to evaluate their effect on the bronchial musculature and were found not to exhibit any significant activity.
Grifantini, M., et al., Farmaco, Ed. Sci. 23(3):197-203 (1968), report the synthesis of several alkyl- and acyl-derivatives of N-amino-1-ephedrine and N-amino-d-pseudoephedrine having antidepressant and monoamine oxidase inhibitory properties.
Jeffrey O'Sullivan et al., Biochimica et Biophysica Acta 1647 (2003) 367-371 report the inhibition of semicarbazide-sensitive amine oxidases by certain aminohexoses, namely glucosamine, galactosamine and mannosamine.
The international patent publications WO 02/020290 and WO 03/006003 disclose certain hydrazino compounds useful as specific VAP-1 SSAO inhibitors that modulate VAP-1 activity. These compounds are described as useful for the treatment of acute and chronic inflammatory conditions or diseases as well as diseases related to carbohydrate metabolism, aberrations in adipocyte differentiation or function and smooth muscle cell function, and various vascular diseases.